Wide angle eyepiece with large eye relief



y 1, 1968 w. H. SCIDMORE ETAL 3,384,434

WIDE ANGLE EYEPIECE WITH LARGE EYE RELIEF Filed April 2, 1965 INVENTORS WRIGHT H.FSCIDMORE United States Patent 3,384,434 WIDE ANGLE EYEPIECE WITH LARGE EYE RELIEF Wright I-I. Scidmore, Langhorne, and Mary D. Flanagan,

3,384,434 Patented May 21, 1968 doublet field lens, a field stop or diaphragm, another type cemented doublet field lens, a singlet center lens and a singlet eyelens, an efiicient and compact wide angle eyepiece having large eye relief will be provided having espe- Philadelphia, Pa., assignors to the United States of 5 clal value m.mihtary vehicles? the like America as represented by the Secretary of the Army speclficifny and referrfng 9 the drawmg, Filed 2, 19 5, s 445 237 sidering our device from the direction from front to rear, 1 Claim. (Cl. 350-208) or towards the direction of eye E, we have provided a cemented doublet field lens of negative power, L and 10 L a field stop or diaphragm D, a cemented doublet field ABSTRACT OF THE DISCLOSURE lens, L and L a singlet center lens, L and a singlet eye- A file-d stop or diaphragm is interposed between a pair lens of cemented doublet field lenses followed by a singlet The data for aforememloned elements or P P center lens and a singlet eyelens to provide a wide angle nents are based on a 9 length of eyeplece eyepiece be 1.000 inch. The ratio of eye relief to focal length 15 approximately 1.175. Our device has been found to work admirably well up to apparent field coverages of about The invention described herein may be manufactured 72. The clear apertures listed in the Lens Table below and used by or for the Government for governmental purj based P a 64 aPParent field as 15 l known poses without the payment to us f any royalty thereon. in the optical art, greatencoverages can be achieved by This invention relates to eyepieces and more particapprflpnately l s thlcknesses fipertures of the ularly concerns optical devices providing an exceptionally Felallve componem s- Since our eYePlece 13 normally used large field of view with a given magnification, in a telescope having another real focal plane, stop or The use of wide angle eyepieces with large eye relief dlaPhragm f be {nade Somewhaf larger to cover is desirable in various military vehicles, such as tanks the full field of view desired so as to eliminate transverse for example, wherein, for purposes of safety of th chromatic aberration at the edges of the stop or diaserver therein, gun recoil or the like may endanger the Phragmeyes or body of the observer due to inadequate clearance The symbols the table below denote the followmg: between the observer and the optical apparatus. It may TABLE I also be necessary that the observer employ cumbersome devices such as gas masks and hence, sighting efficiency L 'the lnilvldual lens will greatly be improved by the use of our device. r the radllls of Curvature It is therefore a principal object of this invention to d a xlal thlckness of lens provide an eyepiecesubstantially possessing the aforespacfi mentioned advantages. refmftwe Index Other objects and advantages will become apparent number of the glass from a consideration of the following specification and F.-total focal length claims and the single figure of the drawing which illusf1,2 a1 length of cemented doublet, L L trates a diagrammatic embodiment of our inventive de- 40 f -focal length of cemented doublet, L -L vice, in axial section. f -focal length of L Briefly, the present invention is based on the discovery f focal length of L,- that by judiciously disposing in axial relation a cemented C.A.clear aperture TABLE IL-LENS TABLE DATA Element Radii Axial Air Space m 0 C.A.

Thickness Thickness d =.063 nl=1.620 vi=6o.3 Li, 2 r2 =+.976

d,=.2s3 m=1.720 v==2aa ==t=oo C.A.2=1.167

l.=.753 D r o C.A.n=1.230 lz=.587 =-3.134 C.A.3=1.343

da=.073 7ta=1.720 v =29.3 L3,; rs=+1.580

d =.5O8 7l4=l.620 l*4=60.3 r1 =-1.5s0 o.A.l=1.505

13=.007 r =+2.50l C.A.s=l.5l3 L5 n.=1.s20 L:,=60.3 (T5) r =5.885 C.A.s=1.484

(T9) l4=.007 r =+1.475 C.A.q)=1.364 L. 18:38:; m=1.620 $60.3

m=+13.l C.(A.s)=l..267

Equivalent focal length, F=1.000". fl and z=--l0.000'. fa and 437.208".

Lens L is of the 'bi-concave type and is cemented to a convex-plano lens L the plane surface of lens Lg being toward the eye E and the combined doublet lens has a divergent effect upon the incident light. This negative doublet has a focal length, i of approximately ment positions the principal plane outside the eyepiece towards the eye and is largely responsible for our inventive large ratio of eye relief or distance to focal length.

Lenses L L L and L; are conveniently made from 620-603 glass whereas lenses L3 and L; are preferably 0 -10.000F which is partially responsible for producing of 720-290 glass. our effective large eye relief. Our device has a Petzval curvature of 0.446, the Petzval The remaining radius of lens L or radius r is 0.320 radius being 2.243F. times the radius r of lens L The air space distance se-pa- We claim: rating lens L; from the diaphragm is 0.753 inch, the 1. A wide angle eyepiece with large eye relief comdiaphragm being located at the paraxlal focus to serve as prising, axially from front to rear, a field stop and to eliminate undesirable stray light as is a cemented doublet field lens of negative power, well known in the art. The field lens elements L and L a diaphragm, is a cemented doublet comprising a bi-concave negative a cemented doublet field lens element L and an equi-convex positive lens L; where the 5 a singlet Center lens, and radii, r and r are equal. The focal length f of the field a Singlet eye lens v s t 1 ii: hiciiieisiigif it? 353 118 5 0? 16221 2355? i e e e a to the follow of its other radius r and the focal length of lens L is table whch dlnenslons are terms of F i and 2.870F. Eyelens L is a meniscus singlet and its long conprocee mg to rear L1 L6 designate-the cave radius, r is the surface closest to the eye and has lenses of sa1d eyeplece '1 H1 deslgnate the radu of a focal length approximating 2.654F. Radius r of eyecllrvaml'e of surfaces f d r spective lenses and said lens L is approximately 0.112 times smaller than radius d1lphragm d1 to e deslgnate F esses f r11. sa1d respective lenses, to 1 designate the axial air space The latter three components, Le. cemented doublet thicknesses between said respective elements, n to u lens L and L and singlets L and L all impart a condesignate the indices of refraction of said respective lenses, verging effect on incident light. Lenses L L and L 1 to :6 designate the Abbe dlspel'slon flllmbers 0f d having positive refracting powers, are placed close to the fespectlve lenses and -0-1 t0 -a dfislgnates e Clear eye whereas the lenses of negative refracting powers are P 0f the respecilvedenses and C-A-D designates placed further from the eye. This aforrnentioned arrangethe clear aperture of sa1d diaphragm:

TABLE IL-LENS TABLE DATA A.'l Al s v on. has... Tessa C.A. =1.l20 n 3050 d.=.os3 n1=1.620 v1=6O.3

d:=.283 F1120 v1=29.3

n C.A.:=1.167

l' =.588 il=.753 CA 1230 D 2=- ca dies n 3'134 d;=.07a m=1.720 v.-.=2s.3 "mi-L580 d4=.508 1n=1.e2o v|=60.3

- =-1.5s0 C.A-|=1.505 1==.007

r, =+2.501 C.(A.)r=1.513

T L; d.=.295 n =1.620 vs=60.3

n =-5.ss5 C-A-5=1.484

r) l4=-007 1' 0=+1.475 C.A.|=1.364

(T10) L. d.=.285 n|=1.620 ts=60.3

"Fa-13.165 C.A.|=1.267

Equivalent focal length, F=1.000'.

No references cited.

DAVID H. RUBIN, Primary Examiner.

R. J. STERN, Assistant Examiner. 

